Psst: it's not another plank.

When you talk about strengthening your core, you’re probably thinking about your abs. In particular, you may be focusing on your rectus abdominus (that’s the six-pack muscle). The rectus abdominus ...

Add Yahoo as a preferred source to see more of our stories on Google. There is an astounding lack of education regarding the true purpose of the muscles in your midsection, and in the interest of ...